Chinese drug companies have been given the opportunity to capture the erectile dysfunction medication market as Pfizer Inc is about to lose its Chinese patent for sildenafi citratel, sold as Viagra.

The US pharmaceutical giant's exclusive right to sell Viagra in China expires in July.

Meanwhile, Chinese companies' generic equivalents are now in the approval pipeline, and hope to get the production green light soon.

One such drugmaker, Guangzhou Baiyunshan Pharmaceutical Co Ltd, is readying its own version of the blue pill for a production license.

"We are not sure whether our ED drug will generate much profit, but we know it is a huge market," Chen Jing, Baiyunshan board secretary, told Shanghai Securities News.

The profits of the new product should reach up to 1 billion yuan (US$162.5 million), a person familiar with the company said.

Since sildenafil is one of Pfizer's major products in the Chinese market, experts said its business performance in China will be affected. Two foreign ED drugmakers, Eli Lilly and Co and Bayer AG, also will be put on notice.

"Booming Chinese drugmakers will promote their versions of the ED product at a much lower price, less than half than that of sildenafil," said Guo Wei an analyst with Ipsos, a global market research company.

Sildenafil reportedly accounted for about 60 per cent of the Chinese market for ED drugs in 2013, compared with a 20 per cent share for the Eli Lilly's Cialis and 10 per cent for the Bayer drug for ED, Levitra.

"In hospitals, sales of ED medication produced by the three foreign companies will be steady because ED medication is a prescription drug," said Guo.

However, Guo pointed out that in the retail channel, cheaper "China-made Viagra" will be popular with consumers.

"Pfizer will continue to offer branded Viagra to ensure that men with ED have ongoing access to a Pfizer medicine that they already know and trust," said Ou Yangjie, senior corporate communication manager at Pfizer Investment Co Ltd.

Ou said in an e-mail to China Daily that Pfizer remains committed to men with ED and continues to invest in innovation to ensure that patients and prescribers have continued access to its products.

According to the 2013 Asia-Pacific Sexual Behaviors and Satisfaction Survey, only 30 per cent of premature ejaculation sufferers in China sought medical treatment, compared with 55 per cent throughout the region.